S&S Cycle
Performance V-Twin Since 1958

Blue Island, Illinois, 1958. George J. Smith and Stan Stankos start a company building high-performance pushrods for Harley-Davidsons out of a small shop south of Chicago. They call it Smith & Stankos — S&S — and the first product is a heat-treated chromoly pushrod that doesn't bend under aggressive cam profiles, which is what every drag racer in the Midwest is asking for that year. It sells. The pushrods turn into cams, the cams turn into carburettors, and within a decade S&S is the name on every fast Harley in the country.

Marjorie Smith — George's wife — buys out Stan Stankos shortly after founding, and the company quietly becomes Smith & Smith. The name on the boxes never changes. In 1969 the operation moves out of suburban Chicago to Viola, a small town in the driftless region of southwest Wisconsin, population about 600. That's still where the head office sits. A second manufacturing facility opened in La Crosse in 2004 to handle the foundry and machining work; the engineering, dyno cells, and testing all stayed in Viola. Current president is Paul Skarie. The company has stayed independent the whole time — never sold to a parent group, never moved offshore.

What S&S sells isn't really individual parts. It's a complete performance ladder for a V-twin Harley. Stage 1 is an intake-and-exhaust kit and a tune. Stage 2 adds cams. Stage 3 brings big bore cylinders and pistons. Beyond that you start replacing the crankcase entirely with an MK or T-series case, and at the top of the stack is the crate engine — a fully assembled motor in a wooden box, dynoed before it shipped, ready to drop into a chassis. Most catalogues claim coverage of all of that. S&S actually delivers it; you can buy every step from the same brand and have it work together.

How S&S Earns the Reputation

Three things, and they're the boring ones. The casting. Crankcases, cylinders, and rocker boxes are cast in Wisconsin to tolerances tighter than the OEM equivalents — you can see the difference if you put an S&S head and a stock head on a surface plate. The dyno cells. Every crate engine is run-in and tuned on a dyno before it leaves the building, and the dyno sheet ships in the box. Most crate engines you can buy elsewhere are assembled-and-shipped; the test cell happens at your installer's expense. The race programme. S&S spent the early 2010s building pro-stock and pro-mod engines for AMA dragbike racing, and that R&D fed back into the catalogue. Today the same engineering team runs the engine programme for Indian's King of the Baggers entries.

For an Iron Stable customer that translates into something specific: when you buy an S&S 124" Power Package, you're getting a part developed against the same internal criteria as the engines that won three KOTB championships. Not because the marketing page says so. Because S&S only has one engineering team.

The crate engine is what S&S is known for. Big steel signs at trade shows, MK136 logos on race bikes, the wooden shipping crate every dealer in America has photographed. But the crate is the top of a much wider engine programme — and most riders never need the top. The 124" Power Package solves the same problem for a third the price.

MK Series — Crate Engines for Milwaukee-Eight

The current flagship. The MK136 and MK136B are 136-cubic-inch (2,232 cc) crate engines built around a new S&S MK case, designed from the start to drop into 2017+ Touring and Softail platforms with M8-style mounting. Black and natural finish options. The 136B variant ships with the 550G cam already installed and dyno-tuned for a flat torque curve. Cooled and oiled to handle continuous touring at full output, not just dyno pulls.

T Series — Twin Cam Long Blocks

The crate engine for 1999–2017 Twin Cam chassis. The T111 (111 ci), T124 (124 ci), and T143 (143 ci, 162 hp, 151 ft-lb) are long-block engines that bolt to the same case mounts as the OEM Twin Cam. T143 is the biggest motor S&S sells for the Twin Cam frame; it'll change a Road King's character completely. Oil-cooled or air-cooled depending on which sub-variant; check the listing.

V Series — Evo Replacement Engines

Pre-1999 Evo and earlier. The V96, V111, and V124 rebuild the older Evo platform with modern internals — same external dimensions, modern crankcase casting, current pistons and rings, dyno-tested before shipping. If you've got a Softail from 1992 with a tired bottom end, this is the route that doesn't compromise on the chassis you've spent twenty years building.

Power Packages — The Bolt-In Big Bore

For people who don't need a full crate motor. The 124", 128", 129", and 132" Power Packages are bore-and-cam kits that fit your existing M8 crankcase. They ship with cylinders, forged pistons, gaskets, head work, and matched cams. Add 11–18 cubic inches without splitting the cases. A workable installer can fit one in a long weekend. Tune is mandatory — every S&S kit needs a Power Vision or equivalent.

X-Wedge — The Custom-Builder Platform

Not a Harley engine. S&S X-Wedge is a 117"–132" V-twin built for custom chopper frames, prostreet builds, and one-off projects — it's the engine that appears in a lot of Arch and West Coast Choppers builds. The catalogue stocks X-Wedge cases, cylinders, and intake parts for builders who want a non-Harley V-twin without building from scratch.

The single biggest characteristic shift you can make to a Harley engine isn't the bore. It's the cam. A 510 cam and a 640 cam in the same 124" Twin Cam build feel like two different motors — one all bottom-end pull, the other a top-end charger. S&S cams are sold in profiles tied to specific use cases, not arbitrary numbers, and the codes tell you what each one is for once you can read them.

Twin Cam — The 475/510/551/585 Family

Twin Cam (1999–2017) takes a pair of bolt-in cams. 475 and 510 are mild upgrades — keep stock springs and pushrods, add 8–12 hp, no other engine work needed. 551 is the popular mid-tier; it's what most Stage 2 builds end up with. 585 is a full Stage 3 cam — needs upgraded valve springs and adjustable pushrods to run safely. Every cam is sold in gear-drive (G/GE) and chain-drive variants — gear is mechanically more accurate at high RPM, chain is quieter and cheaper.

Milwaukee-Eight — The 465/475 + Cam Chest Kits

M8 (2017+) is harder to cam than the Twin Cam — the cam chest is more complex, and the change involves the chain drive plus the inner cam plate. S&S sell complete cam chest kits that include cams, plate, oil pump, and gaskets — one box, one fitting session. The 465 and 475 profiles are the popular M8 grinds; pair them with a 124" or 128" Power Package and the results match a much more expensive crate engine on everything except sustained-load durability.

Cam Codes — How to Read Them

Three numbers and a letter or two. 475G is 0.475" lift, gear-drive. 551GE is 0.551" lift, gear-drive, easy-start (a gentler ramp on the exhaust opening that prevents kickback on high-compression motors). 585R is 0.585" lift, roller. Most installers go GE for anything above 510 lift on a kick-start or push-button-start build over 100 cubic inches. Read the listing carefully — a wrong cam pick is a thousand-pound mistake.